From: Vivek Goyal <vgoyal@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: JeffleXu <jefflexu@linux.alibaba.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
virtualization@lists.linux-foundation.org,
virtio-fs-list <virtio-fs@redhat.com>,
Joseph Qi <joseph.qi@linux.alibaba.com>,
linux-fsdevel@vger.kernel.org
Subject: Re: [Virtio-fs] [PATCH v4 0/8] fuse,virtiofs: support per-file DAX
Date: Tue, 17 Aug 2021 11:19:52 -0400 [thread overview]
Message-ID: <YRvTmIjt/WAl/UOP@redhat.com> (raw)
In-Reply-To: <CAJfpeguA3zeJq-HJUVZHv4nNybqFezkzPNhcWmj0n5+i7YpW4Q@mail.gmail.com>
On Tue, Aug 17, 2021 at 04:11:14PM +0200, Miklos Szeredi wrote:
[..]
> > As for virtiofs, Dr. David Alan Gilbert has mentioned that various files
> > may compete for limited DAX window resource.
> >
> > Besides, supporting DAX for small files can be expensive. Small files
> > can consume DAX window resource rapidly, and if small files are accessed
> > only once, the cost of mmap/munmap on host can not be ignored.
>
> That's a good point. Maybe we should disable DAX for file sizes much
> smaller than the chunk size?
This indeed seems like a valid concern. 2MB chunk size will consume
512 struct page entries. If an entry is 64 bytes in size, then that's
32K RAM used to access 4K bytes of file. Does not sound like good usage
of resources.
If we end up selectively disabling dax based on file size, two things
come to me mind.
- Will be good if it is users can opt-in for this behavior. There
might be a class of users who always want to enable dax on all
files.
- Secondly, we will have to figure out how to do it safely in the
event of shared filesystem where file size can change suddenly.
Will need to make sure change from dax to no-dax and vice-versa
is safe w.r.t page cache and other paths.
Thanks
Vivek
WARNING: multiple messages have this Message-ID (diff)
From: Vivek Goyal <vgoyal@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
virtualization@lists.linux-foundation.org,
virtio-fs-list <virtio-fs@redhat.com>,
linux-fsdevel@vger.kernel.org
Subject: Re: [Virtio-fs] [PATCH v4 0/8] fuse,virtiofs: support per-file DAX
Date: Tue, 17 Aug 2021 11:19:52 -0400 [thread overview]
Message-ID: <YRvTmIjt/WAl/UOP@redhat.com> (raw)
In-Reply-To: <CAJfpeguA3zeJq-HJUVZHv4nNybqFezkzPNhcWmj0n5+i7YpW4Q@mail.gmail.com>
On Tue, Aug 17, 2021 at 04:11:14PM +0200, Miklos Szeredi wrote:
[..]
> > As for virtiofs, Dr. David Alan Gilbert has mentioned that various files
> > may compete for limited DAX window resource.
> >
> > Besides, supporting DAX for small files can be expensive. Small files
> > can consume DAX window resource rapidly, and if small files are accessed
> > only once, the cost of mmap/munmap on host can not be ignored.
>
> That's a good point. Maybe we should disable DAX for file sizes much
> smaller than the chunk size?
This indeed seems like a valid concern. 2MB chunk size will consume
512 struct page entries. If an entry is 64 bytes in size, then that's
32K RAM used to access 4K bytes of file. Does not sound like good usage
of resources.
If we end up selectively disabling dax based on file size, two things
come to me mind.
- Will be good if it is users can opt-in for this behavior. There
might be a class of users who always want to enable dax on all
files.
- Secondly, we will have to figure out how to do it safely in the
event of shared filesystem where file size can change suddenly.
Will need to make sure change from dax to no-dax and vice-versa
is safe w.r.t page cache and other paths.
Thanks
Vivek
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
WARNING: multiple messages have this Message-ID (diff)
From: Vivek Goyal <vgoyal@redhat.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>,
virtualization@lists.linux-foundation.org,
virtio-fs-list <virtio-fs@redhat.com>,
linux-fsdevel@vger.kernel.org,
JeffleXu <jefflexu@linux.alibaba.com>
Subject: Re: [Virtio-fs] [PATCH v4 0/8] fuse,virtiofs: support per-file DAX
Date: Tue, 17 Aug 2021 11:19:52 -0400 [thread overview]
Message-ID: <YRvTmIjt/WAl/UOP@redhat.com> (raw)
In-Reply-To: <CAJfpeguA3zeJq-HJUVZHv4nNybqFezkzPNhcWmj0n5+i7YpW4Q@mail.gmail.com>
On Tue, Aug 17, 2021 at 04:11:14PM +0200, Miklos Szeredi wrote:
[..]
> > As for virtiofs, Dr. David Alan Gilbert has mentioned that various files
> > may compete for limited DAX window resource.
> >
> > Besides, supporting DAX for small files can be expensive. Small files
> > can consume DAX window resource rapidly, and if small files are accessed
> > only once, the cost of mmap/munmap on host can not be ignored.
>
> That's a good point. Maybe we should disable DAX for file sizes much
> smaller than the chunk size?
This indeed seems like a valid concern. 2MB chunk size will consume
512 struct page entries. If an entry is 64 bytes in size, then that's
32K RAM used to access 4K bytes of file. Does not sound like good usage
of resources.
If we end up selectively disabling dax based on file size, two things
come to me mind.
- Will be good if it is users can opt-in for this behavior. There
might be a class of users who always want to enable dax on all
files.
- Secondly, we will have to figure out how to do it safely in the
event of shared filesystem where file size can change suddenly.
Will need to make sure change from dax to no-dax and vice-versa
is safe w.r.t page cache and other paths.
Thanks
Vivek
next prev parent reply other threads:[~2021-08-17 15:20 UTC|newest]
Thread overview: 151+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-17 2:22 [PATCH v4 0/8] fuse,virtiofs: support per-file DAX Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:22 ` [PATCH v4 1/8] fuse: add fuse_should_enable_dax() helper Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:22 ` [PATCH v4 2/8] fuse: Make DAX mount option a tri-state Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:22 ` [PATCH v4 3/8] fuse: support per-file DAX Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:22 ` [PATCH v4 4/8] fuse: negotiate if server/client supports " Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:22 ` [PATCH v4 5/8] fuse: enable " Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:22 ` [PATCH v4 6/8] fuse: mark inode DONT_CACHE when per-file DAX indication changes Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 10:26 ` [Virtio-fs] " Dr. David Alan Gilbert
2021-08-17 10:26 ` Dr. David Alan Gilbert
2021-08-17 10:26 ` Dr. David Alan Gilbert
2021-08-17 13:23 ` JeffleXu
2021-08-17 13:23 ` JeffleXu
2021-08-17 13:23 ` JeffleXu
2021-08-17 2:22 ` [PATCH v4 7/8] fuse: support changing per-file DAX flag inside guest Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:22 ` [PATCH v4 8/8] fuse: show '-o dax=inode' option only when FUSE server supports Jeffle Xu
2021-08-17 2:22 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:22 ` Jeffle Xu
2021-08-17 2:23 ` [virtiofsd PATCH v4 0/4] virtiofsd: support per-file DAX Jeffle Xu
2021-08-17 2:23 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:23 ` Jeffle Xu
2021-08-17 2:23 ` [virtiofsd PATCH v4 1/4] virtiofsd: add .ioctl() support Jeffle Xu
2021-08-17 2:23 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:23 ` Jeffle Xu
2021-08-18 17:33 ` Vivek Goyal
2021-08-18 17:33 ` [Virtio-fs] " Vivek Goyal
2021-08-18 17:33 ` Vivek Goyal
2021-08-17 2:23 ` [virtiofsd PATCH v4 2/4] virtiofsd: expand fuse protocol to support per-file DAX Jeffle Xu
2021-08-17 2:23 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:23 ` Jeffle Xu
2021-08-17 2:23 ` [virtiofsd PATCH v4 3/4] virtiofsd: support per-file DAX negotiation in FUSE_INIT Jeffle Xu
2021-08-17 2:23 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:23 ` Jeffle Xu
2021-08-17 17:15 ` [Virtio-fs] " Dr. David Alan Gilbert
2021-08-17 17:15 ` Dr. David Alan Gilbert
2021-08-17 17:15 ` Dr. David Alan Gilbert
2021-08-18 5:28 ` JeffleXu
2021-08-18 5:28 ` JeffleXu
2021-08-18 5:28 ` JeffleXu
2021-08-19 13:57 ` Dr. David Alan Gilbert
2021-08-19 13:57 ` Dr. David Alan Gilbert
2021-08-19 13:57 ` Dr. David Alan Gilbert
2021-08-18 17:30 ` Vivek Goyal
2021-08-18 17:30 ` Vivek Goyal
2021-08-18 17:30 ` Vivek Goyal
2021-08-17 2:23 ` [virtiofsd PATCH v4 4/4] virtiofsd: support per-file DAX in FUSE_LOOKUP Jeffle Xu
2021-08-17 2:23 ` [Virtio-fs] " Jeffle Xu
2021-08-17 2:23 ` Jeffle Xu
2021-08-17 19:00 ` [Virtio-fs] " Dr. David Alan Gilbert
2021-08-17 19:00 ` Dr. David Alan Gilbert
2021-08-17 19:00 ` Dr. David Alan Gilbert
2021-08-18 5:46 ` JeffleXu
2021-08-18 5:46 ` JeffleXu
2021-08-18 5:46 ` JeffleXu
2021-08-19 13:08 ` Dr. David Alan Gilbert
2021-08-19 13:08 ` Dr. David Alan Gilbert
2021-08-19 13:08 ` Dr. David Alan Gilbert
2021-08-20 5:03 ` JeffleXu
2021-08-20 5:03 ` JeffleXu
2021-08-20 5:03 ` JeffleXu
2021-08-24 10:15 ` Greg Kurz
2021-08-24 10:15 ` Greg Kurz
2021-08-24 10:15 ` Greg Kurz
2021-09-08 10:34 ` JeffleXu
2021-09-08 10:34 ` JeffleXu
2021-09-08 10:34 ` JeffleXu
2021-08-17 8:06 ` [PATCH v4 0/8] fuse,virtiofs: support per-file DAX Miklos Szeredi
2021-08-17 8:06 ` [Virtio-fs] " Miklos Szeredi
2021-08-17 9:32 ` Dr. David Alan Gilbert
2021-08-17 9:32 ` Dr. David Alan Gilbert
2021-08-17 9:32 ` Dr. David Alan Gilbert
2021-08-17 10:09 ` Miklos Szeredi
2021-08-17 10:09 ` Miklos Szeredi
2021-08-17 10:37 ` Dr. David Alan Gilbert
2021-08-17 10:37 ` Dr. David Alan Gilbert
2021-08-17 10:37 ` Dr. David Alan Gilbert
2021-08-17 13:08 ` JeffleXu
2021-08-17 13:08 ` JeffleXu
2021-08-17 13:08 ` JeffleXu
2021-08-17 14:11 ` Miklos Szeredi
2021-08-17 14:11 ` Miklos Szeredi
2021-08-17 15:19 ` Vivek Goyal [this message]
2021-08-17 15:19 ` Vivek Goyal
2021-08-17 15:19 ` Vivek Goyal
2021-08-17 14:54 ` Vivek Goyal
2021-08-17 14:54 ` Vivek Goyal
2021-08-17 14:54 ` Vivek Goyal
2021-08-18 5:10 ` JeffleXu
2021-08-18 5:10 ` JeffleXu
2021-08-18 5:10 ` JeffleXu
2021-08-19 6:14 ` JeffleXu
2021-08-19 6:14 ` JeffleXu
2021-08-19 6:14 ` JeffleXu
2021-08-17 12:40 ` Vivek Goyal
2021-08-17 12:40 ` Vivek Goyal
2021-08-17 12:40 ` Vivek Goyal
2021-09-16 8:21 ` JeffleXu
2021-09-16 8:21 ` JeffleXu
2021-09-16 8:21 ` JeffleXu
2021-09-18 3:06 ` JeffleXu
2021-09-18 3:06 ` JeffleXu
2021-09-18 3:06 ` JeffleXu
2021-09-19 19:45 ` Vivek Goyal
2021-09-19 19:45 ` Vivek Goyal
2021-09-19 19:45 ` Vivek Goyal
2021-09-22 8:16 ` JeffleXu
2021-09-22 8:16 ` JeffleXu
2021-09-22 8:16 ` JeffleXu
2021-08-17 12:39 ` Vivek Goyal
2021-08-17 12:39 ` [Virtio-fs] " Vivek Goyal
2021-08-17 12:39 ` Vivek Goyal
2021-08-17 13:22 ` JeffleXu
2021-08-17 13:22 ` [Virtio-fs] " JeffleXu
2021-08-17 13:22 ` JeffleXu
2021-08-17 14:08 ` Miklos Szeredi
2021-08-17 14:08 ` [Virtio-fs] " Miklos Szeredi
2021-08-18 3:39 ` JeffleXu
2021-08-18 3:39 ` [Virtio-fs] " JeffleXu
2021-08-18 3:39 ` JeffleXu
2021-08-18 5:08 ` Miklos Szeredi
2021-08-18 5:08 ` [Virtio-fs] " Miklos Szeredi
2021-08-18 16:58 ` Vivek Goyal
2021-08-18 16:58 ` [Virtio-fs] " Vivek Goyal
2021-08-18 16:58 ` Vivek Goyal
2021-09-03 5:30 ` JeffleXu
2021-09-03 5:30 ` [Virtio-fs] " JeffleXu
2021-09-03 5:30 ` JeffleXu
2021-09-07 14:51 ` Miklos Szeredi
2021-09-07 14:51 ` [Virtio-fs] " Miklos Szeredi
2021-08-17 14:57 ` Vivek Goyal
2021-08-17 14:57 ` [Virtio-fs] " Vivek Goyal
2021-08-17 14:57 ` Vivek Goyal
2021-08-18 5:20 ` JeffleXu
2021-08-18 5:20 ` [Virtio-fs] " JeffleXu
2021-08-18 5:20 ` JeffleXu
2021-08-30 23:31 ` [Virtio-fs] " Liu Bo
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